This invention relates generally to the field of vehicle seat assemblies and more particularly to a method of forming a vehicle seat having a stylized, contoured surface.
Typically, in the production of a vehicle seat, a forming tool is constructed having a surface contour complementary to the desired shape of the finished vehicle seat or back. One example of such a tool is disclosed in U.S. Pat. No. 4,740,260, issued Apr. 26, 1988, entitled "Method And Apparatus For Manufacturing Seats And Articles Formed Thereby", assigned to the assignee of the present invention. Another method of forming contours in vehicle seat members is disclosed in U.S. patent application Ser. No. 205,929, filed Jun. 13, 1988, entitled "Vehicle Seat Assembly With Pour In Place Foam Body", and assigned to the assignee of this application.
In both the above mentioned application and patent, a vehicle seat cover member is placed inside out on the forming tool. A pressing tool, having contours the same as the desired finished product, then applies pressure against the seat cover member to conform the cover member to the contours of the forming tool. The pressing and forming tools described in the above patent and application must be individually tooled for each new seat design. Accordingly, the tools are relatively expensive to produce.
Along with increased tooling expenses, prior art methods exhibit other limitations. One limitation is the bulk of the machinery required during the pressing stage. A second limitation is the general inability to detect wrinkles in the seat cover member before the bonding of a foam seat bun to the cover member. Elaborate surface contours are still another limitation because of unequal material distribution occurring during the pressing stage.
Forming tools having removable style inserts, which permit the simple modification or changing of the insert instead of the complete replacement of the tool, are described in U.S. patent application Ser. No. 310,351, filed Feb. 14, 1989, and assigned to the assignee of this application. These forming tools allow for the easy interchanging of styles and thus, a reduction in overall tooling costs.
During assembly of a vehicle seat, the seat cover member is placed over the forming tool and drawn into substantial conformity with the style lines or contours of the insert. The drawing of the material is accomplished either by press forming with an appropriately shaped pressing tool or by a vacuum forming process. A foam seat bun is then adhered to the seat cover member with a suitable adhesive.
In order to properly form the desired seat surface, the seat bun must have a predetermined shape corresponding to the style insert used to form the contours in the seat cover member. Thus, different seat buns are required for each different contour style desired in a finished vehicle seat surface.
U.S. patent application Ser. No. 345,789, filed May 1, 1989, also assigned to the assignee of this application, discloses a method for eliminating the requirement of seat buns having a predetermined shape in order to more economically fabricate the finished vehicle seat assembly. The method disclosed in the proceeding patent application first constructs a composite layer by laminating a breathable seat cover member to a polymeric foam sheet. This composite is then cut into a shape appropriate for the style insert being used. A seat skirt fabric is then sewn to the edges of the cover member of the composite. The composite portion is then positioned with the cover member down against the style insert of the forming tool. Next, a sheet of impermeable barrier material is placed over the foam surface of the composite. A vacuum then draws the composite into substantial conformity with the style insert. A flat upper surface of a generic foam seat bun is then sprayed with a suitable adhesive and pressed against the drawn composite. Finally, heat, which can be in the form of steam, is forced through the composite to partially evaporate the barrier. The foam surface of the composite is thus enabled to bond to the foam seat bun.
A problem incurred by the proceeding and other prior art is breathability. Incorporation of the barrier material into the seat construction, as done in vacuum forming, initiates the problem. In some situations the seat is completely non-breathable. This arises when the entire layer of impermeable barrier material remains an element of the seat construction. In other situations the finished seat is semi-breathable. U.S. patent application Ser. No. 345,789, where the barrier material is partially evaporated, displays this limitation.
It is an object of the present invention to eliminate breathability problems while continuing to employ a vacuum forming process. It is another object of the invention to eliminate forming process errors and the various problems associated with elaborate seat designs. In so doing, machinery bulk and tooling costs will also be reduced.
The method according to the present invention first places a seat cover member, exterior side down, over a forming tool. The forming tool can be any of those presently used in the industry which employ vacuum forming.
After the seat cover member is properly positioned, a thin sheet of clear barrier material, such as latex or polyolefin film, is presented over the seat cover member. The barrier material will form an air impermeable layer over the seat cover member and the upper surface of the forming tool. Next, the barrier material and the seat cover member are drawn down into conformity with the style lines of the forming tool by the application of negative pressure across a series of vacuum ports located in the upper surface of the forming tool. Thus, atmospheric pressure is allowed to compress the seat cover member into substantial conformity with the upper surface of the forming tool.
Once the seat cover member is conforming to the upper surface of the forming tool, the vacuum pressure is released. The barrier material is then removed while the seat cover member is maintained in conformity with the upper surface of the forming tool by frictional forces. A visual inspection for discontinuities in the seat cover member can now be conducted.
A foam seat bun, coated with a suitable adhesive such as polyurethane adhesive, is then compressed against and bonded to the seat cover member on the forming tool. Once the cover member is bonded to the foam seat bun, the assembly is removed from the forming tool for completing the construction of the seat assembly.
The above described method can easily be adapted for use with various types and styles of forming tools, including those having the changeable inserts. The above method can also be adapted for use with the various styles of foam seat buns, premolded or the generic type having stylized composite inserts. Additionally, the method can be easily adapted to construct seat backs.
Thus, the method for forming a portion of a vehicle seat assembly according to the present invention may be summarized as including the following steps:
a. placing a seat cover member exterior side down on a forming tool having an upper surface complimentary to the desired surface contour of the finished seat assembly; PA0 b. combining a layer of barrier material with the seat cover member on the forming tool; PA0 c. drawing a vacuum between the forming tool and the barrier material; PA0 d. drawing the seat cover member and the barrier material into substantial conformity with the upper surface of the forming tool; PA0 e. applying an adhesive to the appropriate surface of a foam seat bun; PA0 f. releasing the vacuum between the forming tool and the barrier material; PA0 g. removing the barrier material from the seat cover member and forming tool; PA0 h. inspecting the seat cover member visually for wrinkles and other discontinuities; PA0 i. pressing the adhesive laden surface of the foam seat bun against the seat cover member on the forming tool; and PA0 j. removing the foam seat bun and bonded seat cover member from the forming tool, thus forming a portion of a vehicle seat assembly having the desired styled surface contour. Further objects, features and advantages of the present invention will become evident from a consideration of the detailed description when taken in conjunction with the accompanying drawing and the appended claims.